Elapsed time indicator

ABSTRACT

An elapsed time indicator or delay switch including a cylindrical housing of non-magnetic material closed at one end by a base of magnetic material. A pair of spaced apart electrically conducting terminals insulated from and extending into and through the base. A permanent magnetic piston slidably positioned within the housing, spaced from said base and having a viscous fluid therebetween. A pressure releasable piston retainer disposed above the piston for limiting the movement thereof and a flexible deformable diaphragm, proximate the retainer, closing the opposite end of the housing. The device is initiated upon pressure being applied to the diaphragm which thereupon deflects the retainer and releases the piston that in turn is attracted toward the base and moves theretoward at a rate dependent, among other factors, on the fluid viscosity, the magnetic force, initial spacing and the clearances between the housing and the piston. Piston travel terminates upon contact with the inner terminals and electrical shorting thereof which may be used to indicate the end of the elapsed period.

United States Patent Porter, J r, et a1.

I ELAPSED TIME INDICATOR Inventors: Frank K. Porter, Jr., Billerica; Boris Sonjara, Sudbury, both of Mass.

The United States of America as represented by the Secretary of the Army Filed: Dec 7,1971 Appl. No.: 205,586

Assig-nee:

[56] References Cited UNITED STATES PATENTS Clason Dube et al. ..'...335/240 FOREIGN PATENTS OR APPLICATIONS 361,852 6/1962 Switzerland ..200/83 .1

12/1959 Brauneck ..335/62 [57] ABSTRACT An elapsed time indicator or delay switch including a cylindrical housing of non-magnetic material closed at one end by a base of magnetic material. A pair of spaced apart electrically conducting terminals insu lated from and extending into and through the base. A permanent magnetic piston slidably positioned within the housing, spaced from said base and having a viscous fluid therebetween. A pressure releasable piston retainer disposed above the piston for limiting the movement thereof and a flexible deformable diaphragm, proximate the retainer, closing the opposite end of the housing. The device is initiated upon pressure being applied to the diaphragm which thereupon deflects the retainer and releases the piston that in turn is attracted toward the base and moves theretoward at a rate dependent, among other factors, on the fluid viscosity, the magnetic force, initial spacing and the clearances between the housing and the piston. Piston :travel terminates upon contact with the inner terminals and electrical shorting thereof which may be used to indicate the end of the elapsed period.

governmental purposes without the payment to usof any royalty thereon.

BACKGROUND OF THE INVENTION The present invention relates to timing or switching devices and more particularly pertains to elapsed time indicators or time delay switches of the hydromagnetic type wherein the period commences upon release of a piston which is magnetically coupled to a fixed element and moves through a viscous fluid toward the element. In the field of timing and delay switch mechanisms, it

has been the general practice to employ relatively structurally complex and expensive devices for oneshot applications. Such devices have proved to be relatively unsatisfactory in that they are bulky, complex and subject to breakdown over extended periods of storage.

SUMMARY OF THE INVENTION 'releasably held by a retainer across the opposite end of the housing. A flexible diaphragm closes the open end whereby when pressure is applied to the diaphragm it will activate the retainer to release the piston which in turn will be magnetically drawn toward the disc through the fluid and upon reaching a position proximate the disc will short the conductors.

An object of this invention is to provide a reliable,

small, low cost, simple and indicator or switch.

. Another object is to provide a hydromagnetic time delay switch which exhibits a broad timing range, an unlimited storage life and requires no external motive energy source.

Still another object is the provision of an elapsed time indicator which may be initiated in a number of easily operable elapsed time ways, can operate in a physical position and is selfsustaining upon initiation.

Other objects and many of the attendant advantages 7 of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection I with the accompanying drawing wherein the single FIGURE is a cross-sectional view of an embodiment made in accordance with invention.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT In the illustrated embodiment of the drawing the elapsed time indicator or delay switch 10 includes a generally cylindrical or hollow housing 11 open at both the principle of the present.

ends which is of a non-magnetic material including plastics. The lower'end of 'the housing is sealed or closed by a disc 12 of a magnetic material such as iron and is provided with spaced apart openings 13 and-14 these extending therethrough. Passing through openings and into the housing are electrical conductors l5 and 16 which are sealed therein and electrically insulated therefrom by a potting or bonding material 17 and 18 with exposed terminals 19 and 20 directed into the housing. Disposed within the housing for sliding movement lengthwise therein is a permanent magnet piston 21 which is magnetically drawn toward the disc or base but restrained from such movement by a releasable retainer 22. This retainer may be of a light spring material, to function as a trigger, and extends across the. top of the piston and partially in between the inner wall of the housing and the outer peripheral surface of the piston. The upper face 23 of the piston is formed with a central' recess 24 which provides a void into which the retainer spring can be deflected. The upper open end of the housing is closed by a flexible diaphragm 25. The pleniumor cavity intermediate the lower face 26 of the piston and the inner surface 27 of the disc 12 is filled with a viscous fluid 28.

It is clear from the foregoing that either the piston or the disc may be a magnet and that various configurations and triggers are equally well suited for the intended purposes.

Summarizing, the self-contained device which when installed and initiated can sense the elapsed time and indicate it through the triggering of an electrical or mechanical utilization circuit 29. The device is suitable for a remote single operation installation where it may be required to be dormant for a long period, but it can also be employed for these applications requiring attendance and repeatability.

The basic ,device includes a cylinder, fabricated of non-ferrous material and sealed at oneend with a disc of iron. Mounted axially to this disc through a non-conductive bond material are two metal pins which protrude equal distances into the cylinder. cavity and externally away from the disc. This forms the switch contacts which are normally open. A piston, fabricated from a permanent magnet material, is inserted into the cylinder such that a cavity remains between the face of the piston and disc of iron. The piston is restrained in this position by a light spring material trigger which is attached to the piston and engages the piston and the rim of the cylinder to trap it or by some other means applicable to the installation. The cavity is then filled with a viscous fluid.

To initiate the device an external build-up of pressure is used to deflect the diaphragm which then bears against the light spring trigger until it is finally deformed to the position where it no longer restrains the piston. The influence of the magnetic properties in its attraction to the iron disc are now free to function causing a translation of the piston toward the iron base. The viscous fluid impedes this translation since it must be expelled from the cavity through the orifice available to it, namely, the clearance between piston and cylinder walls. The time consumed or elapsed for this translation is a function among others, of fluid viscosity, magnetic attraction, initial gap, and clearances between Piston and cylinder.

The piston ends its'translation when it rests against the insulated pins in the disc. The greater influence of the magnetic attraction at this proximity to the disc material, aids in forming a short circuit or electrical path between the two pins. This switch function can be used to signal the end of the elapsed time.

it should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as setforth in the appended claims.

, We claim:

' 1. A time delay switch comprising:

a housing of non-magnetic material,

apiston slidable in said housing of a material to provide a permanent magnetic coupling with,

an element fixedly supported within said housing,

a viscous fluid confined between said piston and said element, I

means for releasably holding said piston spaced from said element and,

a switch means for indicating proximate relation between said element and said piston.

2. The switch according to claim 1 .wherein saidhousing is a hollow cylinder and said piston is of a permanent magnet.

3. The switch according to claim 2 whereinsaid element is a disc of magnetic material closing one end of said cylinder.

4. The switch according to claim 3 wherein said switch means includes a pair of electrically spaced apart conductors passing through, sealed to, and insulated from said disc and extending into said cylinder.

5. The switch according to claim 3' wherein said means for releasably holding is a spring retainer disposed across the top of said piston engaging the inner wall of housing and releasing said piston upon application of pressure thereto.

6. The switch according to claim 5 wherein said piston is formed with a central recess opposite said retainer.

7. The switch according to claim 6 further including a flexible diaphragm closing the opposite end of said cylinder proximate said retainer. 

1. A time delay switch comprising: a housing of non-magnetic material, a piston slidable in said housing of a material to provide a permanent magnetic coupling with, an element fixedly supported within said housing, a viscous fluid confined between said piston and said element, means for releasably holding said piston spaced from said element and, a switch means for indicating proximate relation between said element and said piston.
 2. The switch according to claim 1 wherein said housing is a hollow cylinder and said piston is of a permanent magnet.
 3. The switch according to claim 2 wherein said element is a disc of magnetic material closing one end of said cylinder.
 4. The switch according to claim 3 wherein said switch means includes a pair of electrically spaced apart conductors passing through, sealed to, and insulated from said disc and extending into said cylinder.
 5. The switch according to claim 3 wherein said means for releasably holding is a spring retainer disposed across the top of said piston engaging the inner wall of housing and releasing said piston upon application of pressure thereto.
 6. The switch according to claim 5 wherein said piston is formed with a central recess opposite said retainer.
 7. The switch according to claim 6 further including a flexible diaphragm closing the opposite end of said cylinder proximate said retainer. 